1. Technical Field
The present invention relates generally to a volumetric measuring apparatus, and more particularly to an improved structure of a volumetric measuring apparatus which measures the volume of a liquid material stored within a container by subtracting the volume of gas filling an empty portion of the container from the volume of the container.
2. Background Art
Japanese Patent First Publication No. 59-164916 teaches a volumetric measurement system which has a pair of volume-changing means and a pressure sensor means. The volume-changing means are disposed within a liquid-stored container and a reference enclosure communicating with the container. The pressure sensor means detects pressures in the container and the reference enclosure independently. The volume of the liquid in the container is determined based on a ratio of the pressures in the container and the reference enclosure.
In order to detect the pressures in the container and the reference enclosure, the above prior art volumetric measurement system teaches two pressure sensors mounted in the container and the reference enclosure, respectively. As an alternative form, a single pressure sensor and a directional control valve are also proposed. In this arrangement, the pressure sensor communicates with the container and the reference enclosure through separate pressure lines. The directional control valve switches between the pressure lines to detect the pressures in the container and the reference enclosure separately. These prior art arrangements, however, result in a complex structure of the volumetric measurement system, increasing manufacturing costs.